Method of and apparatus for treating aqueous solution of electrolytes



June 10, 1947. H. 1.. TIGER METHOD OF AND APPARATUS FOR TREATING AQUEOUS SOLUTION .OF ELECTROLYTES' Filed Dec. 9, 1942 2 Sheets-Sheet 1 CATION EXCHANGE UNIT ACID REMOVAL UNIT HOWARD L TIGER INVENTOR.

BY M44 ATTORNEY H. L. TIGER June 10, 1947.

METHOD OF AND APPARATUS FOR TREATING AQUEOUS SOLUTION OF ELECTROLYTES 2 Sheets-Sheet 2 Filed Dec. 9, 1942 HOWARD L. TIGER INVENTOR.

A14 ATTORNEY Patented June 10,

UNITED STATE I 1,422,054- s PATENT oF cE METHOD OF AND APPARATUS FOR TREAT- .ING AQUEOUS SOLUTION OF ELECTRO- LYTES Howard L. Tiger flewlett, N. Y., assignor to The Permutit Company, New York, N. Y., a corporation of Delaware ApplicationDecember 9, 1942, Serial No. 468,348

This invention relates to a method of and apparatus for treating an aqueous solution of electrolytes; and it comprises removing electrolytes from such solution by successive and repeated passage of predetermined volumes of the solueralizing the solution, 1. e. removing electroytes from it. The solution to be treated is first passed through a bed of granular cation exchange material charged with hydrogen ions and thence through a bed of granular anion exchange or acid removal material charged with --hydroxyl ions. On passing through the cation exchange ,material the metallic cations of the salts contained in the solution to be treated are exchanged for hydrogen ions so that the solution then contains free mineral acids such as hydrochloric,

sulfuric, carbonic and other acids formed with whatever anions are present in the solution undergoing treatment. Upon passage of this acid solution through the bed of acid removal material the free mineral acids are removed; the carbonic acid, which is notabsorbed by the acid removal material to any appreciable extent, may

be eliminated. by the simple expedientof aeration if CO2 is undesirable in the use to which the treated solution is to be subjected.

The best way of carrying out this process of demineralizing is to place a bed of each of the ion exchange materials into a tank provided with the valves and connections required to control flow through the tanks.

The ion exchange materials used in this method of electrolyte removal become exhausted after a certain extent of use, and they must then be recharged with the kind of ion serving their particular purpose. To this end, the cation exchange material is regenerated with dilute acid, such as sulfuric or hydrochloric acid, while the acid removal material is regenerated with the dilute solution of an alkali, such as caustic soda,soda ash, sodium bicarbonate, ammonium hydroxide or the like. After regeneration the ion exchange materials must be freed by rinsing of excess regenerant and the products resulting from the regenerating reactions.

14 Claims. (01.- 21o-24) g trolytes. By a single passage of the solution through cation exchange and acid removal material, an-efliuent meeting such rigorous specifications can, as a rule, not be obtained at all, or at bestonly in relatively small quantities, if the solution. to be treated contains large amounts ofsulfates and chlorides. In an attempt to solve this" problem the sug estion has been made in the patent to Riley No. 2,267,841, dated Dec. 30,1941, to recycle a portion of the demineralized solution. discharged by the acid removal unit during normal'service, mixing this recycled solution with j the rawsolution supplied to the cation exchange unit. In this manner more complete electrolyte removal is obtained than by single passage operation since such recycling dilutes the raw solution 1 with a solution from which the major proportion of dissolved electrolytes has been removed, so

that the solution supplied to the cation ex- For many uses, such as the treatment of water change unit has an electrolyte contentsubstantially lower than that of the raw solution. While this process of recycling a portion of the effluent improves matters considerably, it is still not an altogether satisfactory solution of the problem because not all of the available capacity ofthe cation exchange and acid removal materials can be utilized since the run must be interrupted and the units regenerated as soon as the concentration of electrolytes in the effluent exceeds the predetermined limit. Furthermore, to meet exacting specifications the major portion of the eiliuent must be recycled, making the apparatus relatively large and expensive.

It is an object of this invention to provide a method of and apparatus for demineralizing a solution so thoroughly as to meet the most rigorous requirements, regardless of the concentration of electrolytes in the untreated solution; another object is to utilize the available capacity of the demineralizing materials to the fullest extent possible; another object is to improve the economies of regeneration; a further object is to attain the aforesaid objects with a relatively small apparatus; and still another object is to provide an apparatus functioning with a minimum amount of attention on the part of the operator.

The manner in which these objects are achieved is illustrated in the appended drawings in which:

Fig 1 is a diagrammatic view, partly in section, of an apparatus according to this invention and adapted to carry out the process of this invention;

Fig. 2 is a modification of certain portions of the apparatus of Fig. 1;

Fig. 3 is another modification of certain portions of the apparatus of Fig. 1; and

Fig. 4 is a wiring diagram for the apparatus of Fig. 1 to provide automatic operation thereof.

Like numerals refer to like parts throughout 'the'several views.

Referring now to Fig. 1, a cation exchange unit comprises a tank i3 containing a bed ll of granular organic cation exchange material. Associated with tank I3 is a tank i2 containing regenerating solution, e. g. dilute sulfuric acid. A supply pipe II for solution to be treated is fitted with a valve l4 and communicates with a pipe l5 leading to the top of tank l3 and fitted with a valve l3. A backwash outlet |1 provided with a valve I3 is connected to pipe l5. A pipe IS with valve 23 leads from pipe l3 to the bottom of tank It and also communicates with a rinse outlet 2| provided with a valve 22. An injector 23 communicates with supply Pipe l3 through pipe 24 with valve 25 and also has a suction pipe 23 leading into tank l2 and fitted with a valve 21, and a discharge 23 leading into tank I3 above the top of bed An acid removal unit comprises a tank 33, containing a bed 3| of granular acid removal material which may be organic anion exchange material such as synthetic resin or inert material impregnated with synthetic resin adapted to remove free mineral acid from solution. A tank 32 containing a dilute solution of an alkali such as caustic soda, soda ash, sodium bicarbonate, ammonium hydroxide or the like, is associated with tank 30. A supply pipe 33 connected to pipe l3 communicates with a pipe 35 leading through a valve 33 to the top of tank 33. A pipe 34 leads from supply pipe |3 through a valve 43 to a pipe 33 connected with the bottom of tank 33. A backwash outlet pipe 31 with valve 33 communicates with pipe 35, and a rinse outlet 4| with valve 42 communicates with pipe 33. An injector 43 has a supply pipe 44 fitted with a valve 45 and communicating with supply pipe 33, a suction connection 43 leading into tank 32 and fitted with valve 41, and a discharge 43 leading into tank 33 above the top of bed 3|.

A meter 53 for determining the electric conductivity of a solution is connected by means of a pipe 5| with the pipe 33 so as to receive a sample therefrom. The tested solution is discharged through a pipe 52 to a suitable point of disposal. It may, of course, be returned to pipe 33.

The pipe 33 has two discharge connections 54 and 55 fitted with valves 53 and 51, respectively, and each arranged to discharg into one of two receiving tanks 53 and 53, as shown. The receiving tanks 53 and 53 have outlet pipes 35 and 33 fitted with valves 61 and 33, respectively. Pipes 65 and 33 are connected with a. suction pipe 33 of a pump 10. The pump 13 has a discharge pipe 1| fitted with a check valve 12 and con- 4 the top of tank 33, down through the acid removal material 3|, and finally through pipes 33 and 54 into the receiving tank 53. When a quantity of water has thus been collected in tank 53 the flow of water is stopped by closing valves l4 and 53.

' The pump 13 is started, and valves 51, 31 and nected to a return pipe 14 leading through a valve 15 to the supply pipe I3, and to a pipe 13 leading through a valve 11 to an elevated storage tank 18 which has an outlet 13 leading to a point of use. In the upper portion of storage tank 18 a degasifier is provided, comprising a head 30 carrying a plurality of nipples 8|, and spaced horizontal slats 82 arranged in superimposed tiers. An air blower 33 is connected by means of a duct 34 with the air space below the slats 32.

The operation of the apparatus shown in Fig, 1 will now be described. Let it be assumed that the solution to be treated is raw water of high electrolyte content supplied to pipe l3. In placing the apparatus in operation, valves l4, I3, 33 and 53 are opened, all other valves being closed. Water now flows via pipes l3 and I5 to the top of tank It, down through the cation exchange material thence via pipes I3, 33 and 35 to 15 are opened, all other valves remaining as before. The water is now pumped from tank 53 via pipes 35, 33, 1| and 14 into the supply pipe i3, passing through the cation exchange and acid removal units a second time, and discharging through pipe 55 into the receiving tank 53. When the entire batch of water has thus been transferred from tank 53 to tank 53, valves 51 and 31- are closed and valves 53 and 33 are opened. Thereupon the water is pumped from tank 53, passing successively through the cation exchange and acid removal units a third time, and discharging into tank 53. This re-passing is repeated by alternately opening either valves 51 and 31 or 53 and 33, and closing the other pair oi said valves, until the meter 53 shows that the water flowing through pipe 33 and sampled through pipe 5| has an electric conductivity corresponding to an electrolyte content low enough for the intended use.

Assuming that when this happens the batch of water is in tank 53, then valves l4, I3, 33, 51, 31 and 11 are opened, all other valves being closed. (If the batch of water should happen to be in tank 59, valves 53 and 33 would have to be opened instead of valves 51 and 31.) Now the treated water from tank 53 is pumped via pipes 35, 33, 1| and 13 to the top of the elevated storage tank 13. It is distributed by the nipples 8| and cascades over the slats 32, encountering a counter flow of air discharged by the blower 33 through duct 84 and escaping through the nipples 3|. Dissolved CO2 is thus effectively removed from the water which may then be withdrawn from the tank 13 via pipe 13 as needed. Simultaneously with the withdrawal of treated water from tank 53, a. new batch of raw water admitted from pipe i3 is passed successively through the cation exchange and acid removal units and collected in the receiving tank 53.

When all treated water has been removed from tank 53, valves 31 and 11 are closed. When, furthermore, another batch oi. water of suflicient volume has been collected in tank 53, valves l4 and 51 are closed, and valves 56, 58 and 15 are opened, so that the new batch is pumped from tank 53 through the cation exchange and acid removal units into tank 58. This re-passing is repeated by manipulating valves 53, 51, 31 and 33, as described above. Having made the batches relatively large, it will be found by observing the reading of meter 53, that after 2 or 3 passes the electrolyte content of the water flowing through pipe 33 has not reached a sufliciently low value and does not drop appreciably even upon repeated re-passing. This indicates that the cation exchange and acid removal materials have been exhausted and require regeneration.

Preparatory to regeneration all valves of the apparatus are closed and the pump 13 is stopped, the partly treated batch of water undergoing treatment being retained in either one of the two receiving tanks 53 and 53. In the following description of the cycle of regenerating operations only the valves to be opened in each of the individual steps will be referred to, it being understood that all valves not specifically mentioned in any particular step of the regenerating cycle are closed.

g na,

wardly through the material and to waste via pipes I and I1. This is continued for about minutes, until the wash water discharged by pipe I1 is clear.

Second, the cation exchange unit is regenerated by opening valves 22, 25 and 21. Raw water from pipe I3 flows through pipe 24 to the injector 23, drawing acid regenerant from tank I2 through pipe 28, and the diluted regenerant passes through pipe 28 to the upper portion of tank I8, downward through the material II, and to waste, via pipes I9 and 2|. This is continued until a sufiicient quantity of regenerant has been injected.

Third, the cation exchange unit isrinsed by opening valves I4, I6 and 22. Raw water flows from pipe |3 through pipe I5 to the top of tank I8, downward through the material II, and to waste via pipes I9 and 2|. This is continued until the unit has been rinsed suificiently free of spent and excess regenerant.

Fourth, the acid removal unit is backwashed by opening valves 38 and 49. Raw water flows from pipe I3 via pipes 34 and 39 into tank 39, up through the material 3|, and to Waste through pipes 35 and 31. This-is continued for a few minutes, until the wash water discharged by pipe 31 Is clear.

, Fifth, the acid'removal material is regenerated -by opening valves l4, I5, 42, 45 and 41. Raw water from pipe I3 flows through pipe I5, the cation exchange material pipes I9, 33 and 44 to the injector 43, drawing alkali solution from tank 32 through pipe 46, and the diluted regenerant passes through pipe 48 to the upper portion of tank 39, downward through the material 3|, and via pipes 39 and 4| to waste. This is continued until a suflicient quantity of regenerant has been injected.

Sixth, the acidremoval material is rinsed by opening valves I4, I6, 36 and 42. Raw water from pipe I3 now flows through pipe I5, the cation exchange material H, pipes I9, 33 and 35 to the'top of tank 38, down through the acid removal material 3|, and via pipes 39 and 4| to waste. This is continued until the water flowing through pipe 39 has an electrolyte content approximately equal to that of the raw water. Such water, while not suitable for use, may be mixed with the stored, partly treated batch of water since the mixture will be subjected to further treatment, as will presently be described.

The six steps of the regeneration process are carried out successively in the order named, ex-

cept that the third step (rinsing the cation exchange material) and the fourth step (backwashing the acid removal material) may be carried out concurrently, if so desired.

Regeneration of both ,units being completed, the further treatment of the stored, partly treated batch of water is resumed. To this end pump 19 is started, and valves I6, 36 and as Well as either valves 55 and 58 or 51 and 51 (depending upon whether the partly treated batch of water had been stored in tank 59 or 58, respectively) are opened, all other valves being closed. Re-passing of the batch of water through the two units is continued by appropriate manipulation of valves 55, 51, 51 and 68 until the meter 58 indicates that the desired low electrolyte content has been reached.

Thereupon, as previously described, the treated batch of water is passed from the one receiving tank to the storage tank while simultaneously another new batch of water is admitted from pipe I3 through the two treatment units to the other receiving tank. The batch is then further treated by repeated re-passing through the two treatment units until they are exhausted whereupon they areregenerated. Then the new batch is again passed through the units until the treatment is completed. Thus the cycle of operations is repeated, each regenerating cycle being interspersed in successive passes of one batch of water.

Fig; 2 shows a modification of certain portions of the apparatus of Fig. 1. Here the receiving tank 58 is connected with a point of use (through a pump, degasifier and elevated storage tank, if desired) by a pipe 88 fitted with a valve 89. The pump 10 is connected to draw from the receiving tank 59 through a pipe 85, and to discharge into the supply pipe I3 through a return pipe 85. Within tank 59, and underneath the discharge pipe 55 is a bafiie or overflow trough 81 to prevent, as much as possible, mixing of the entering liquid with liquid contained in tank 59.

In the operation of the modification shown in Fig. 2 only those steps will be described which are different from those set forth above in connection with Fig. 1. When starting operation, valves I4 and 51 are opened until a predetermined batch of water has been collected in tank 59. Then valve I4 is closed and pump 10 is started, causing the water in tank 59 to be pumped via pipes 85 and 85 through the cation exchange and acid removal units and through pipe 55 'back into tank 59. Thus, the batch of water may be passed repeatedly through the two units as often as desired without changing any valve settings. When the cation exchange and acid removal units are exhausted this re-passing is interrupted by closing valve 51 and stopping pump 18, to be resumed after regeneration of the two units has been completed, As soon as the electrolyte content of the batch undergoing treatment has reached the .desired low valve, valve 51 is closed and valve 55 opened so that the treated water is discharged into the tank 58. When the entire batch of water has thus been transferred from tank 59 to tank 58, the pump 10 is stopped, valve 56 is closed. and valves I4 and 51 are opened, admitting a new batch of water to tank 59 and thus starting a new cycle of operations. While this new batch is being treated, the previously treated water may be withdrawn from tank 58 via pipe 88 as needed.

In the modification shown in Fig. 3 a single receiving tank 98 is used. The pipe 39 is arranged to discharge selectively into this tank through a pipe 9| under control of a valve 92, or to a point of use through a pipe 95 fitted with a valve 96, The pump 18 has a suction pipe 93 connected with tank 90 and a discharge ipe 94 connected with the supply pipe I3. A baffle or overflow trough 91 is placed underneath the discharge pipe 9| for the purpose noted in'connection with Fig. 2. If a continuous and uninterrupted supply to service is required, a storage tank must be provided in the service pipe 95, an additional provision of a degasifier and service pump being optional.

In operation of the apparatus shown in Fig. 3, valves I4 and 92 are opened to admit water via the treating units to tank 90. As soon as a predetermined batch has been collected in tank 9|), valve I4 is closed and the pump 19 started. Then this batch of water is passed from tank 98 via pipes 93 and 94 to the treatment units and thence through pipes 39 and 9| back into tank 90 as long as necessary to obtain the desired quality of treated water, this operation being interrupted by closing valve 92 and stopping pump 10 when the treatment materials have been exhausted and require regeneration. When treatment of a batch has been completed valve 92 is closed and valve opened so that the batch of water is pumped through the treatment units and via pipe 95 to service, As soon as tank 90 has thus been emptied, this cycle of operations is repeated.

It will be noted that in the arrangements of Figs. 2 and 3 the solution may be passed through the treatment units as many times as desired without requiring any attention whatsoever, whereas in the arrangement of Fig. 1 the valves 56, 51, 61 and 68 must be manipulated every time the batch of solution has been passed through the treatment units. This apparent advantage in favor of the arrangement of Figs. 2 and 3 is offset, however, by the disaadvantage that a larger number of passes is'required than with the arrangement of Fig. 1 to produce treated solution meeting given specifications, because in spite of the provision of the baflles or overflow troughs 81 and 91, respectively, some mtermingling of newly admitted and previously treated solution takes place in tanks 59 and 90, respectively, so that certain portions of each batch are passed through the units more often than others. Such intermingling cannot take place in the arrangement of Fig. 1 wherein the solution, in each passing, is taken from one receiving tank and discharged into the other. It follows, therefore, that an apparatus of given size, while requiring somewhat less attention, will require a longer time to treat a given volume of solution, or in other words, will produce a lesser quantity of treated solution in a given time, when the solution receiving means of Figs. 2 or 3 are used rather than the receiving means shown in Fig. 1. Thus, each of the three modifications shown has certain advantages and disadvantages as compared with either of the others, and choice of the type of arrangement to be used in any particular case will best be governed by a consideration of local conditions.

While not necessary for the practice of this invention, it is highly desirable for convenient and efficient operation that both the cation exchange unit and the acid removal unit are matched as to capacity so as to become exhausted and ready for regeneration at the same time. The cation exchange unit removes metallic cations, whereas the acid removal unit removes chlorides and sulfates, as a rule a lesser quantity in equivalent terms. Therefore, the ratio of the quantity of cation exchange material to the quantity of acid removal material is best determined in each case so as to match approximately the ratio of total metallic cations to the sum of chlorides and sulfates in the solution to be treated. If, in the course of operation, the ratio of metallic cations to chlorides plus sulfates in the solution being treated should decrease or increase somewhat, then the quantity of regenerant used in regenerating the cation exchange material or acid removal material, respectively, may be reduced. In this manner the operator is able to change the ratio of cation exchange capacity to acid removal capacity of a given installation to match, within certain limits, a change in the ratio of metallic cations to the sum of chlorides plus sulfates in the solution undergoing the treatment.

In practicing this invention it is preferable to make the volume of each batch of solution such that it contains a quantity of electrolytes equal to the electrolyte removal capacity, between regenerationsmf the cation exchange and acid removal materials, or one-half, one-third, 'etc., of such capacity, in other words, a simple fraction in which the numerator is unity. This has the advantage that the times at which the treatment materials become exhausted and ready for regeneration remain in step with the times at which treatment of one batch is completed and that of another batch started. Such coordination of regenerations and batch replacements renders operation of the apparatus more orderly and convenient, and makes for maximum economy in the use of regenerants. The coordination may be effected by providing either one of the following programs: Staggering the regenerations and batch replacements; i. e. arranging regeneration to take place between successive passes of a batch, assetforth in the foregoing description, or synchronizing the regenerations and batch replacements, i.'e. arranging regeneration to take place at a time when treatment of a batch has been completed and before treatment of the next batch is started.

The process of this invention may appropriately be referred to as multiple demineralizing in view of the characterizing feature that each batch of solution is passed repeatedly through the treatment units. This term applies regardless of whether or not regenerations and batch replacements are coordinated, and whether a program of staggered or synchronized regenerations and batch replacements is followed.

In order to obtain a clear picture of the merits of multiple demineralizing according to this invention over the prior art processes the tests presently to be described were carried out. These tests were made under laboratory conditions because they permit more accurate control of all variables than is possible in a full size plant. The electrolyte solution treated was raw water, the analysis of which is as follows, expressed in P. P. M. as 'CaCOz:

and ready for regeneration at about the same time. The bed of cation exchange material had a diameter of 3.5 cm. and consisted of 400 ml. of granular organic hydrogen cation exchanger (sulfonated coal); the regenerant was 1200 ml. of 0.403 N H2SO4. The bed of acid removal material had a diameter of 2.3 cm. and consisted of 200 ml. of granular synthetic resin acid remover; the regenerant used for this bed was 280 ml. of 0.75 N NazCOs solution. In all the tests the beds were backwashed and rinsed in a uniform manner, and one-half hour was taken to introduce the quantities of regenerant noted above. In treating the water the rate of'fiow was ml. per minute. The electrolyte content of the treated water was determined by means of an electric conductivity meter, and the results are given in terms of P. P. M. NaCl. The following six methods of demineralizing were tested under the conditions set forth above:

First, the well known method of demineralizing by a single passage of the water'through cation exchange and acid removal material. The treated water was collected in portions of 500 ml. each, and it was -found that the first portion contained about 50 P. P. M. of electrolytes (expressed as NaCl) the second portion 24, the third portion about 60, and the fourth and last portion about 300. In other words, with a raw water of as high an electrolyte content as that used in these tests, single pass operation furnishes treated water of a quality not meeting stringent specifications.

Second, recycling to the cation exchange unit three-fourths of the water discharged by the acid removal unit, in accordance with the method suggested in Riley Patent 2,267,841. The treated water was collected in successive portions of 100 ml. each. About 800 ml. of the treated water was found to have an electrolyte content of P. P. M. or less, the average of the 800 ml. being 6.6 P. P. M. and the lowest value obtained in any of the 100 ml. portions being 4.5 P. P. M.

Third, the method outlined in the foregoing paragraph, except that five-sixths of the water discharged by the acid removal unit was recycled. About 900 ml. of the treated water had an elec- 10 izing in accordance with this invention (tests 4 to 6), as compared with demineralizing methods heretofore known tests 1 to 3), spectacular inand where the requirements as to quality are not exceptionally stringent, these materials have capacities, between regenerations, of about 275 and 600 m. eq. per 1., respectively. Such normal capacities are not obtainable when demineralizing high electrolyte waters .in accordance with previously known methods (tests 1 to 3). By multiple demineralizing of high electrolyte water in accordance with this invention, using synchronized regeneration (test 4) a cation exchange catrolyte content of 10 P. P. M. or less, the aver- I age of the 900 ml. being 4.0 P. P. M., and the lowest value obtained in any of the 100 ml. portions being 2.9 P. P. M.

Fourth, multiple demineralizing in accordance with this invention by passing a batch of 2000 ml. three times through the treatment units, regeneration and batch replacement being synchronized. The treated water was found to have an electrolyte content of 3.0 P. P. M.

Fifth, multiple demineralizing in accordance with this invention by passing a batch of 3000 ml. four times through the treatment units, regeneration and batch replacement being staggered (regeneration after three passes). The treated water had an electrolyte content of 4.3 P. P. M.

Sixth, the method outlined in the foregoing paragraph, except that the batch was passed through the treatment units six times. The treated water had an electrolyte content of less than 1 P. P. M.

For a clear comparison of these test results, which in every case are typical of a number of consecutive cycles of operations, the significant data are summarized in the following tabulation.

Quantity Electrolyte content of treated of treated water water 'res Method of dernineralgf g g N 0. mm; used in test content Average I Owesf not exof stated a ceeding qimntity 10 p. p. m.

. M. P. P. M. P. P. M.

l Single pass 0 24 2 Recycling three-fourths 800 6.6 4. 5

(Riley Patent 2,267,-

841) 3 Recycling five-sixths (Riley Patent 2,267,-

841) 900 4. 0 2. 9 4 Multiple demineralizing, synchronized regeneration, 3 passes... 2,000 3.0 3. 0 5 Multiple demineralizing, staggered regeneration, 4 passes 3, 000 4. 3 4. 3 6 Multiple demineralizing, stag ered regcnoration, 6 passes 3, 000 1. 0 1. 0

pacity of about 290 m. eq. per 1. and an acid removal capacity of about 570 in. eq. per 1. were obtained. Thus, by my improved method, using synchronized regeneration, it is possible to obtain, under abnormally severe operating conditions, capacities which areapproximately equal .to capacities obtained by earlier methods under normal conditions. With the use of staggered regeneration (tests 5 and 6), however, the cation exchange capacity was as high as about 42-5 m. eq. per 1. and the acid removal capacity about 850 m. eq. per 1. In other words, by multiple demineralizing in accordance with myinvention, using staggered regeneration, cation exchange and acid removal capacities are obtained under abnormally severe conditions which exceed by as much as 55 and 40 per cent, respectively, normal capacities obtained by the use of formerly known methods under normal conditions. The reason for this startling improvement incapacity may be understood by considering the properties of ion exchange materials. Directly after regeneration, and upon rinsing'out all: spent and excess regenerant from the material, ions are exchanged or removed from the solution undergoing treatment quite thoroughly. In other words, the metallic cation content in the case of cation exchange, or the content of anions of acids (except carbonic acid) in the case of acid removal, in the treated solution is quite low, approaching zero when the concentration of such ions in the raw solution is not very high. As the treatment progresses this thorough exchange or removal continues quite uniformly for some time. However, as the limit of capacity of the ion exchange material is approached, the ion exchange becomes less and less complete. That is to say, the concentration, in the treated solution, of ions which are to be removed in the process, rises gradually, slowly at first and then increasingly faster. When, in the ordinary use, the concentration of the treated solution has thus risen to the limit permissible in any particular case, the treating operation is terminated and the ion exchange material is regenerated. This means, of course, that a substantial portion of the ultimate exchange capacity remains unused and is wasted. It is this normally unused portion of the capacity which is utilized by the program of staggered regeneration-in accordance with this invention. In this method a batch of raw solution is passed 11 through partly exhausted material until the ion exchange practically ceases. The fact that the ion exchange is incomplete does not matter for, subsequent to regeneration, the same batch oi solution will be passed through freshly regen-- able after substantially complete exchange ceases varies for different exchangers. With most materials it amounts to as much as about 50 per cent of the normally usable capacity, thus accounting for a corresponding increase in capacity obtained in the tests with staggered regeneration over that obtained with synchronized regeneration.

One drawback of my method oi multiple demineralizing, especially with staggered regeneration, is the relatively large number of valve manipulations required at various times during each cycle of operations, necessitating more or less continuous attention on the part of an operator. This objection may be overcome by automatic control of the various valves.

Fig. 4 shows electrical operating and control equipment for providing automatic operation of the apparatus of Fig. 1. Only those devices of Fig. 1 are included in this diagram which are necessary for an understanding of the automatic operation. In this arrangement the sequence and timing of the various steps of each cycle are controlled by a motor driven drum switch mechanism D, a motor driven cam type time switch mechanism T, a ratchet relay R, a solenoid switch S,

a pair of mechanically latched-in solenoid switches SI and S2 with electrically operated release, float switches FI and F2 mounted on regenerating solution tanks I2 and 82, respectively, float switches F3 and F4 mounted on receiving tank 58, float switches F5 and F6 mounted on receiving tank 58, manually operated switches MI and M2, and a switch I operated by the meter 50 to close when the conductivity oi the sample being tested does not exceed a predetermined low value, and to open when the conductivity exceeds said value. The valves I4, I6, I8, 20, 22, 25, 21, 36, 38, 40, 42, 45, 41, 56, 51, 61, 68, I and 11 are operated by solenoids IOI, I02, I03, I04, I05, I06, I01, I08, I08, IIO, III, H2, H3, H4, H5, H6, H1, H8 and H8, respectively. The valves are of the normally closed type, that is to say they are opened by energization of the solenoids, and they close when the solenoids are deenergized. The pump 10 is driven by an electric motor I20.

The drum switch mechanism D has a drum' I2I made of insulating material (shown in developed form) and adapted to be rotated in the direction of the arrow I22 by a motor I23 through a speed reducer I24. On drum I2I are mounted contact strips I25 to I46 inclusive, all electrically interconnected by the branched wire I41, and also a contact strip I48 with a lateral extension I48. The switch mechanism D also has brushes I50 to I86 adapted to variously make contact with strips I25 to I46 and I48 in nine diflerent operating positions of the drum I2I, and brushes I66 to I14 which, upon rotation of the drum I2I, are successively contacted by the lateral extension 8. The time switch mechanism T comprises a constant speed motor I80 which is adapted t rqt t 12 a shaft I8I through a speed reducer I82. The shaft I8I carries cams I88, I84, I86, I86 and I81 having notches I88, I88, I80, I8I and I82, respectively. Switches I88 to I81 are controlled by the cams I 88 to I81, switch I83 being opened when its stem drops into notch I88, whereas switches I84, I85, I86 and I81 are closed when their stems rliggp into the respective notches I88, I80, I8I and The ratchet relay R has a solenoid 200 adopted, upon each energization thereof, to move a pawl 20I an amount sumcient to advance a ratchet wheel 202 one tooth. The ratchet wheel 202 has nine teeth and is mounted on a shaft 203 which also carries a cam 204 having three notches 205. A switch 208 controlled by the cam 204 is normally open and closes when the stem 201 drops into any one 0! the notches 205. Thus, switch 206 is closed by each third successive energization of the solenoid 200, and maintained open by the intermediate two enerzizations of the solenoid.

The solenoid switch 8 has a coil 2I0 which, upon energization, opens normally closed switches 2H and 2I2.

The solenoid switch SI has an operating coil 2 I5 which, upon energization, closes switches 2I6, 2" and 2I8. when coil H5 is subsequently deenergized the switches 2I6, 2" and 2I8 remain closed because of the iunction of a mechanical latch-in mechanism not illustrated), to be opened only when release coil 2I8 is energized. Solenoid switch S2 is of similar construction as switch SI, comprising an operating coil 220, switches 22I, 222 and 223, and a release coil 224.

Float switch FI has a float 230 actuating a switch 23I in such manner that the switch is open when tank I2 is full, and closes when the float 230 has dropped to a predetermined level, in other words, after a predetermined quantity of regenerant has been withdrawn from tank I2. Float switch F2 is of similar construction, having a switch 235 actuated by a float 236 which rides on the regenerating solution in tank 32 and closes switch 235 when a predetermined quantity of solution has been withdrawn.

Float switch F3 has a float 240 which closes switches MI, 242, 243 and 244 when the liquid in tank 58 has reached a predetermined high level, and, which opens these switches when the level of solution has dropped a relatively small amount, say one or two inches below said high level. Float switch F4 has a float 245 actuating switches 246 and 241 in such manner that switch 246 is opened and switch 241 is closed when tank 58 is practically empty (containing just enough liquid to prevent the float 245 from touching bottom), but that switch 246 is closed and switch 241 opened when the level in tank 58 rises a small amount.

Float switch F5 is similar to switch F3, having a float 250 which closes switches 25I, 252, 253 and 254 when tank 59 contains a predetermined volume of liquid and which opens these switches when the tank contains less liquid. Float swtch F6 is similar to switch F4; it has a float 255 which opens switch 256 and closes switch 251 when tank 58 is nearly empty, and reverses the position of both switches as soon as the level of liquid has risen a small amount.

Manual switches MI and M2 have switch members 260 and 261 adapted to be placed so as to connect the respective terminals 262 and 263 selectively with the terminals marked Hand and Auto.

Pipe 54 is fitted with a valve 210 so actuated by a float 21! riding on the liquid in tank 58 as to close when the level rises by a small. margin beyond the level at which float 240 closes the switches 24I to 244. Pipe 55 is similarly fitted with-a valve 280 which is closed by a float 28I when the liquid in tank 59 rises beyond the level at which float 250 closes switches 25I to 254.

Electric power is supplied from a source (not shown) through wire 300 which is grounded, and wire 30I which has branches connected with brush I50, the right hand contact points .of switches I94, I95, I96, I91, 2, 2I2, 235 and 24I, the Hand terminals of switches MI and M2, and the left hand contact points of switches 23I and 25I.

Solenoids IOI to H3, H8 and H9 are grounded through the branched wire 302. Motors I20, I23 and I80 are grounded at 303, 304 and 305, respectively. Solenoid coils II4, II5, H6, H1, 200, 2I0, 2I5, 2I9, 220 and 224 are grounded through wires 3I0, 3II, 3I2, 3I3, 3I4, 3I5, 3I6, 3I1, 3I8 and 3I9, respectively. All these motors and solenoids are thus electrically connected with wire 300.

The brushes" II to I14 have connections as follows: brush I5I by wire 320 with solenoid IOI;

brush I52 by wire 32I with solneoid I02; brush I53 by branched wire 322 with solenoids I03 and I04; brush I54 by wire 323 with solenoid I05; brush I55 by branched wire 324 with solenoids I06 and I01; brush I56 by wire 325 with solenoids I08; brush I51 by branched wire 326 with solenoids I09 and H0; brush I58 by wire 321 with solenoid III; brush I59 by branched wire 328 with solenoids H2 and H3; brush .160 by wire 329 with solenoid II8; brush I6I by branched wire 330 with solenoids H9 and 2I0; brush I62 by branched wire 33I with the left hand points of switches 2I6 to 2I8 and the right hand points of switches 22I to 223; brush I63 by branched wire 332 with the right hand points of switches I93 and 252 and the left hand point of switch 242; brush I64 by branched wire 334 with motor I80 and the left hand point of switch I93; brush I65 by'wire 335 with motor I23; brush I66 by branched wire 33.6 with the left hand point of switch 254 and the right hand point of switch 244; brush I61 by wire 331 with the right hand point of switch I00; brush I68 by wire 336 with the left hand point of switch I91; brush I69 by wire 339 with the left hand point of switch 235; brush I10 by wire 340 with the left hand point of switch 'I96; brush "I by wire 34I with the left hand point of switch I95; brush I12 by wire 342 with the right hand point of switch 23; brush I13 by wire 343 with the left hand point of switch I94; and brush I14 by wire 344 with the left hand point of switch 206.

The apparatus, furthermore, includes the following connections: branched wire 350 connecting solenoid 200 with the right hand point of switch 242 and the left hand point of switch 252; wire 35! interconnecting the left hand points of switches 2I I and 243; wire 352 interconnecting the left hand point of switch 2I2 and the right hand point of switch 253; branched wire 353 interconnecting the left hand points of switches I00 and MI with the right hand points of switches 206 and 25I; branched wire 354 connecting the left hand point of switch, 353 with solenoids 2I9 and 220; branched wire 355 connecting the right hand point of switch 243 with solenoids 2I5 and 224; branched wire 356 connecting the right hand point of switch 2I6 with solenoid H6 and the Auto. terminal of switch MI; branched wire 361 connecting the left hand point of switch 22I with the solenoid H1 and the Auto. terminal of switch M2; wire 356 interconnecting the right hand points of switches 2I1 and 241; wire 359 interconnecting the left hand points of switches .222 and- .251; wire 360 interconnecting the right hand points of switches 2I0 and 246; wire 36I interconnecting the left hand points of switches 223 and 256; wire 362 connecting the left hand point of switch 244 with the right hand point of switch 251; wire 363 connecting the left hand point of switch 241 with the right hand point of switch 254; branched wire 364 connectingthe motor I20 with the left hand point of switch 246 and the right hand point of switch 256; wire 365 interconnecting solenoid H4 and terminal 263 or switch M2; and wire 366 interconnecting solenoid II5 and terminal 262 of switch MI.

In the following description of the operation of the apparatus of Figs. 1 and 4 the various flow paths of the solution will be referred to but briefly, having been traced in detail in describing manual operation of the apparatus shown in Fig. 1.

It will be noted that brush I50 is permanently in contact with strip I25 as the drum I2I rotates so that strips I 26 to I46 are at all times in electrical connection with supply wire 30I through brush I50, strip I25 and branched wire I41. For the sake of brevity the various electrical circuits will, therefore, be described only starting with any of the strips I26 to I46, it being under? stood that the circuits extend to these strips from supply wire 30I via brush I50, strip I25 and branched wire I41. In a like manner, the circuits will be described up to any of the ground connections 302 to 305'a'nd 3I0 to 3I9 only, it being understood that the circuits continue from these connections to the supply wire 300. In actual practice, as a matter of fact, it will usually be found preferable to extend branches of the supply wire 300 directly to the connections 302 to 305 and 3I0 to 3I9.

In Fig. 4 the control devices are shown in the positions which they occupy when treatment of' one batch of solution has just been completed, the batch being contained in receiving tank 59. A circuit is established from strip I26 through brush I5l, wire 320 and solenoid IOI to ground connection 302, opening valve I4. A second circuit from strip I30 through brush I52, wire 32I and solenoid I 02 to ground 302 opens valve I6. A third circuit from strip I35 through brush I56, wire 325 and solenoid I08 to ground 302 opens valve 36. A fourth circuit starting at strip I4I goes via brush I6I and branched wire 330 on the one hand through solenoid II 9 to round 302, opening valve 11, and, on the other hand through solenoid 2I0 to ground 3,I5, opening switches 2H and 2I2. A fifth circuit starts at strip I42 and goes through brush I62 and branched wire 33I to switches 22I and'223; from switch 22I the circuit continues through wire 351, branching through solenoid M1 to ground 3l3, and through switch member 26I, terminal 263, wire 365 and solenoid II4 to ground 3I0, thus openin valves 68 and 56; from switch 223 the circuit continues through wire 36I, switch 256, wire 364 and motor I20 to ground 303, so that pump 10 runs.

With valves I4, I6, 36, 56, 68 and 11 open, and pump 10 running, the treated solution is pumped from tank 59 to the storage tank 18 (Fig. 1), while at the same time a new batch of solution is being admitted to tank 58. The new solution maintains switch I in closed position. Switch- I00 will, therefore, be opened. As soon as some solution has been withdrawn from tank 59 float switch F will open. Neither of these switch changes, however, will have any effect on the established circuits, and both the above stated flows of solution continue until the treated batch has been withdrawn from tank 59 and a full new batch has been admitted to tank 58. Both these events will never occur at exactly the same time, and, depending on which occurs first, the sequence of operations will be somewhat different. It is desirable, however, that the rate of flow at which the new batch is introduced be somewhat greater than the rate at which the treated batch is being withdrawn. This is accomplished by providing valve 11 with a port opening smaller than that of the other valves. The same result could also be obtained by limiting the movement of valve 11 so that it cannot open wide, or by installing an orifice or other flow limiting device in pipe 16. When the level in tank 58 has risen to a predetermined height float 240 closes the switches 2 to 244. This still does not alter the established circuits inany way. After a small additional rise in level the float 21I closes valve 210 (which is preferably of the quick closing type), thus terminating the flow into tank 58 which now contains an accurately measured new batch of solution. A short time thereafter the treated solution will have been withdrawn from tank 59 to "the extent that float 255 opens switch 256 and closes switch 251. The opening of switch 256 breaks the circuit through motor I20, stopping pump 10, while the closing of switch 251 establishes a circuit from strip I42 through brush I62, wire 33I, switch 222, wire 359, switch 251,

wire 362, switch 244, wire 336, brush I66, strip I48,- brush I65, wire 335, and motor I23 to ground 304.

Motor I23 runs and rotates drum I2I in the direction of the arrow I22 until brushes I50 to I65 contact the drum I2I along line B-B at which time the motor I23 stops because the extention I49 has moved out of contact with brush I66, coming to rest in contact with brush I14. In this new position of drum I2I brushes I5I and I6I have moved out of contact with strips I26 and HI, respectively, thus breaking the circuits through solenoids IOI, H9 and 2I0 so that valves I4 and 11 and switches 2H and 2I2 close. The closing of switch 2 establishes a circuit from line 30I via switch 2, wire I, switch 243 and branched wire 355, thence through solenoids 2I5 and 224 to the respective ground connections 3I6 and 3I9; the energization of operating solenoid 2| 5 closes switches 2I6 to 218 while the energization of the release solenoid 224 opens switches 22I to 223. The opening of switch 22I deenergizes solenoids H4 and H1, closing valves 56 and 68. Brushes I52 and I56 remain in contact with strips I30 and I-35, thus maintaining the previously described circuits through solenoids I02 and I08 so that valves I6 and 36 remain open. Brush I62 remains in contact, with strip I42, and brushes I60 and I63 have moved into contact with Strips I39 and I43, respectively. Thus a circuit is established from strip I39 through brush I60, wire 329 and solenoid II3 to the ground 302, opening valve 15. Another circuit runs from strip I42 through brush I62 and wire 33I to switches 2I6 and 2I6; from switch 2I6 the circuit continues via 16 branched wire 356 through solenoid II6 to the ground 312, and through switch member 260,

terminal 282, wire 366 and solenoid I I5 to ground 3I I, opening valves 61 and; from switch 2I8 the circuit continues through wire 360, switch 246, wire 364 and motor I20 to ground 303, thus again starting pump 10. Still another circuit runs from strip I43 through brush I63 to wire 332 and then divides itself. one branch going through switch I93, wire 334 and motor I to ground 305, while the other branch continues through switch 242, wire 350 and solenoid 200 to ground 3I4. The motor I now rotates shaft I8I in the direction indicated by the arrows until the stem of switch I93 drops into notch I88 of cam I83 whereupon switch I93 opens, stopping motor I80. During the rotation of shaft I8I cam I81 has opened switch I91. Thus the stop-' ping of motor I80 leaves the time switch mechanism T in its zero or starting position in which all its switches I93 to I91 are open. The energization of solenoid 200 pulls pawl 20I upwardly, advancing ratchet wheel 202 one tooth and turning cam 204 so that notch 205 moves away from the stem 201 of switch 206 which, therefore, opens.

Valves I6, 36, 51, 61 and 15 being open, the solution is now pumped from tank 58 into tank 59, passing through the treatment units a second time. As the level in tank 58 drops float 240 soon opens switches 24I to 244. The opening of switch 242 deenergizes solenoid 200 which permits pawl 20I to drop, to be thus ready for another actuation. The opening of switch 243 deenergizes solenoids 2I5 and 224, but switches 2I6 to 218 remain nevertheless in closed position because of the mechanical latch-in mechanism previously mentioned. When the batch of solution has been transferred to tank 59 float 250 closes float switch F5. At such.time the level in tank 58 has not dropped sufl'llciently to change the positioning of float switch F4. This is so because after the previous closing of float switch F3 an additional small quantity of solution had been admitted up to the level at which float valve 210 closed, and this small quantity is now left in tank 58 in addition to another small quantity equal to that which had been left in tank 59 at the time float switch F6 had moved to terminate the withdrawal of the previously treated batch oi solution to the storage tank 18. It is to be understood that fioat switches F3 and F5 are adjusted to be closed upon admission of approximately equal volumes of solution to the tanks 58 and 59, respectively, and that float switches F4 and F6 are likewise adjusted to stop further withdrawal of solution when about equal volumes have been withdrawn from the tanks. The closing of float switch F5 establishes a circuit from strip I43 through brush I63, wire 332, switch 252, wire 350, and coil 200 to the ground 3I4, advancing the ratchet wheel 202 a second tooth. It also establishes a circuit from wire 30I through switch 2I2, wire 352, switch 253 to wire 354, and thence in divided paths through solenoids 2I9 and 220 to the respective grounds 3" and 2 I8. The energization of solenoids 2I9 and 220 opens switches the opening of switch 2I3 and the simultaneous closing of switch 223 the connection between wires 33I and 364 is simply transferred from switches 2I8 and 246 to switches 223 and 256 so that the motor I20 remains energized and pump 10 continues to operate.

Now valves I6, 36, 56, 68 and 15 are open and the batch of solution is pumped from tank 59 to tank 58, passing throughthe treatment units a third time. As the level inta'nk 59 drops float 250 opens switches 25I to 254, -breaking the circult through solenoids 200, 2 I9 and 220, The pawl 20I drops, but switches 221 to 223 are retained in their closed position by the latchin mechanism of switch S2. As soon as the batch of solution being treated has been transferred to tank 68 float 240' closes switches 24I to 244, the position of float switch F6 remaining unchanged for the reason previously'given with regard to float switch F4. The closing of switch 243, as previously explained, energizes solenoids 2I5 and 224, opening switches 22I to 223 and closing switches 2I6 to 2I8 whereby solenoids H4 and H1 are deenergized and solenoids H5 and H6 energized, closing valves 56 and 68 and opening valves 51 and61. Furthermore, the circuit for the motor I20 is transferred from switches 223 and 256 to switches 2I8 and 246. The closing of switch 242 energizes solenoid 200, as described previously, and the ratchet wheel 202 is advanced a third tooth so that the stem 201 of switch 206 drops into one of the notches 205, closing the switch. This establishes a circuit fromwire 30I through switch 24I, wire 353, switch 206, wire 344, brush I14, strip I48, brush I65, wire 335 and motor I23 to ground 304. (It should be noted that if the solution should be in tank 59 at the time switch 206 closes this circuit would include switch 25I instead of MI, and the positions of switches SI, S2, F3 and F5 as well as that of valves 56, 51, 61 and 68 would be reversed.)

The motor I23 rotates drum I2I until the brushes I50 to I65 make contact along line -0 when the circuit through motor I23 is broken by the extension I49 leaving brush I14 and coming to rest in contact with brush I13. Solenoids M and 224 remain energized but all other previously existing circuits are now broken as strips I30, I35, I39, I42 and I43 move out of contact with brushes I52, I56, I60, I62 and I63, respectively. Therefore, all previously open valves close, the pawl 202 drops, and the pump motor I 20 stops. The following circuits are established: from strip I21 through brush I5I, wire 320 and solenoid IOI to ground 302, opening valve I4; from strip I32 through brush I53, branched wire 322 and solenoids I03 and I04 to ground 302, opening valves I8 and 20; and from strip I44 through brush I64, wire 334 and motor I80 to ground 305. Motor I80 thus slowly rotates shaft I8I, cam I83 soon closing switch I93.

With valves I4, I8 and 20 open the cation exchange un is being backwashed until, after an appropria e interval of time, determined by the rotational speed of shaft I8I and the angular setting of cam I84 on the shaft, the stem of switch I94 drops into notch I89, closing switch I94. This establishes a circuit from supply wire 30I through switch I94. wire 343, brush I13, strip I48, brush I65. wire 335 and motor I23 to ground 304. The motor I23 then rotates drum I2I until the brushes I50 to I65 make contact along line D-D when the circuit through motor I23 is broken because the extension I49 leaves brush I13 and comes to rest in contact with brush I12. Strips I21, I32 and 18 I44 are moved out of contact with brushes 'I5I, I53 and I64, respectively, thus breaking all circuits, Valves I4, I8 and 20 close, and motor I stops. Two new circuits are established: from strip I33 through brush I54, wire 323 and solenoid I05 to ground 302, opening valve 22; and from strip I 34 via brush I55 and branched wire 324 to solenoids I06 and I01, and thence to ground 302, opening valves 25 and 21.

Valves 22, 25 and. 21 being open, regenerating solution from tank I2 is injected into the cation exchange unit. When the required amount of solution has been withdrawn from tank I2 float switch FI closes and establishes a circuit from supply wire 30I through switch 23I, wire 342,

brush I12, strip I48, brush I65, wire 335 and motor I23 to ground 304. The motor I23 then rotates drum I2I until switches I50 to I 65 make contact along line E-E when extension I49 leaves brush I12, breaking the circuit through motor I23, and comes to rest in contact with brush I". In this position strip I34 has left brush I55, closing valves 25 and 21. Strip I33, however, remains in contact with :brush I54, keeping valve 22.0pen. Another circuit runs from strip I28 through brush I5I, wire 320 and solenoid IN to ground 302, opening valve I4. A third circuit goes from strip I3I through brush I52, wire 32I and solenoid I02 to ground 302, opening valve I6. Still another circuit runs from strip I45 through brush I64, wire 334 and motor I80 to ground 305 so that motor 30 again rotates shaft I8I, soon opening switch With valves I4, I6 and 22 open the cation exchange unit is being rinsed free of spent and excess regenerant until, after lapse of a predetermined interval of time, the stem of switch I drops into notch I90, closing switch I95. This establishes a circuit from supply wire 30I through switch I95, wire 34I, brush I1I, strip I48, brush I65, wire'335 and motor I23 to ground 304. The motor I23 now rotates drum I2I until extension I49 passes-from brush "I to brush I10 when the circuit through motor I23 is broken and the drum stops with brushes I50 to I65 making contact along line FF. In this position only the cirouit starting at strip I45 is maintained, keeping the timing motor I80 in operation which'soon opens switch I95. All other previously existing circuits are broken so that valves I4, I6 and 22 are closed. A new circuit is established from strip I 36 via brush I51 to branched wire 326, and thence through solenoids I09 and H0 to the ground 302.

With valves 38 and 40 thus opened the acid removal unit is backwashed until the stem of switch I96 drops into notch I9I. This establishes a circuit from the supply wire 30I through switch I96, wire 340, brush I10, strip I48, brush I65,

wire 335 and motor I23 to ground 304. Motor I23 then rotates the drum I2I vuntil the brushes I50 to I65 make contact along line G'G when the circuit through motor I23 is broken as extension I49 passes from brush I10, coming to rest in contact with brush I69. In this position strips I36 and I45 have been moved out of contact with brushes I51 and I64, opening valves 38 and 40 and stopping motor I 80. The following circuits are established: from strip I29 through brush I5I, wire 320 and solenoid IOI to ground 302, opening valve I4; from strip I30 through brush I52, wire 32 I and solenoid I02 to ground 302, opening valve I6; from strip I31 through brush I58, wire 321 and solenoid I II to ground 302, opening valve 42; and from strip I38 through brush I59 to branched wire 328, and thence through solenoids H2 and "3 to ground 302, opening valves 45 and 41.

Valves I4, I6, 42, 45 and 41 being open, regenerating solution from tank 32 is introduced into the acid removal unit. When the required amount of regenerating solution has been withdrawn from tank 32 float switch F2 closes and establishes a circuit from supply wire 30I through switch 235, wire 339, brush I69, strip I48, brush I65, wire 336 and motor I23 to ground 304. The motor I23 rotates the drum I2I until brushes I50 to I65 make contact along line H-H when extension I 49 breaks the circuit through motor I23 by passing from brush I69 to brush I68. In this position strip I38 is out of contact with brush I59, closing valves 45 and 41. The circuits starting at strips I29, I30 and I31 are maintained so that valves I4, I6 and 42 stay open. Two new circuits are established: one from strip I36 through brush I56, wire 325 and solenoid I08 to ground 302, opening valve 36; and another from strip I46 throughbrush I64, wire 334 and motor I80 to ground 305. Motor I80 once more rotates shaft I'8I, and the cam I86 shortly opens switch I96.

Now valves I4, I6, 36 and 42 are open, and spent and excess regenerant is being rinsed from the acid removal unit until, after a predetermined interval of time the cycle of regenerating operations is completed when the stem of switch I91 drops into notch I92. Thereby, a circuit is established from supply wire 30I through switch I91, wire 338, brush I68, strip I48, brush I65, wire 335 and motor I 23 to ground 304. The motor I23 rotates the drum I2I until the brushes I50 to I65 contact the drum along line I--I when the circuit through the motor is broken as extension I49 passes from contact with brush I68 and comes to rest in contact with brush I61. In this position the circuits starting at strips I29, I31 and I46 are broken so that valves I4 and 42 close, and motor I80 stops. The circuits starting at strips I30 and I35 are maintained, and valves I6 and 36 thus remain open. Valve 15 is opened by a circuit passing from strip I'40 through brush I60, wire 329 and solenoid II8 to ground 302. Another circuit starting at strip I42 runs through brush I62 and wire 33I to switches 2I6 to 2I8 which are still closed, solenoids 2I5 and 224 having remained energized all the while; from switch 2I6 the circuit continues through wire 356 and then branches through solenoid II6 to ground 3I2, and through switch member 260, terminal 262, wire 366 and solenoid II to ground 3| I, opening valves 61 and 51; from switch 2I8 the circuit continues via wire 360, switch 246,

wire 364 and motor I20 to ground 303, placing pump once more in operation.

With valves I6, 36, 51, 61 and open and pump 10 in operation thecondition existing immediately prior to the start of the regenerating cycle has been restored (except that the ratchet relay R is now rendered inoperative because brush I63 has no contact), and the partly treated solution retained in tank 58 is pumped from tank 58 through the treatment units into tank 59. When the level in tank 58 has dropped a small amount, switch F3 opens, deenergizing solenoids 2I5 and 224 which, however, does not change the positions of switches SI and S2. When the batch of solution has been transferred to tank 59 float switch F5 closes, energizing solenoids 2 I9 and 220 so that switch SI opens while switch S2 closes. Thereby valves 51 and '61 are closed and valves 56 and 68 opened so that the solution is pumped 20 from tank 59 through the treatment units into tank 58. Float switch F5 opens upon withdrawal of a small amount of solution from tank 59, deenergizing solenoids 2I9 and 220.

" Now let it be assumed that while the solution is thus being passed a filth time through the treatment units it reaches the desireddegree of purity. The electric conductivity of the sample going to meter 50 through pipe 5| will then be low enough to cause switch I00 to close. Nothing happens immediately. However, as soon as float switch F3 closes upon transfer of the entire batch oi. solution to tank 58, it not only energizes solenoids 2I5and 224, closing switch SI and opening switch S2 and thereby closing valves 56 and 68 and opening valves 51 and 61, and transferring the circuit for motor I20 from switches 223 and 256 to switches 2I8 and 245, but also establishes a circuit from supply wire I through switch 24I, wire 353, switch I00, wire 331, brush I61, strip I48, brush I65, wire 335 and motor I23 to ground 304. The motor I23 rotates the drum I2I once more until the brushes I to I65 make contact along line AA when the circuit for motor I23 is broken by the passing of extension I49 from brush I61, coming to rest in contact with brush I 66. In other words, the drum I2I has now returned to the position initially described and shown in Fig, 4 and one entire cycle 01' operations has been completed. All the devices, however, are not in the same position which they occupied initially, the position of switches SI, S2, F3 and F5 being reversed because the treated batch of solution is now in tank 58 whereas at the end of the preceding cycle it had been in tank 59.

With valves I4, I6, 36, 51, 61 and 11 open, a new batch oi. solution is admitted to tank 59 until float valve 280 closes while the treated 5 tinues under entirely automatic control.

When the apparatus is first installed tanks 58 and 59 are both empty and float switches F3 and F5 open so that neither of valves 56 and 51 can open. To initiate operation the drum I2I is placed so that brushes I50 to I65 make contact along line A-A. This opens valves I4, I6 and 36 by circuits previously described. Then the switch member 26I oi manual switch M2 is moved to the Hand position, establishing a 60 circuit from supply wire 30I through member 26I, terminal 263, wire 365 and solenoid II4 to ground 3I0 which opens valve 56. This admits solution through the treatment units to tank 58. When the level has risen to a height where float 85 245 closes switch 246 and opens switch 241 the 7 a circuit from supply wire 30I via switch member switch member 26I is returned to Auto. position, breaking the circuit and closing valve 56. Then the switch member 260 of manual switch MI is moved to "Hand position, establishing 260, terminal 262, wire 366 and solenoid I I5 to ground 3 which opens valve 51. Float switch F5 is then observed, and as soon as it moves to closed position the switch member 260 is returned to "Auto." position, breaking the circuit so that valve I1 closes. This places in both receiving tanks the quantities of solution required for proper functioning of the control devices. Then the cam 204 of ratchet relay R is turned manually to a position in which the stem 20! is in one of the notches 205, and the drum III is moved to the next position in which brushes I50 to I65 make contact along the line B-B; this may be done by means of a hand crank or a manual switch of the same type as switches MI and M2 (not shown). Coil 220 of switch S2 is now energized, closing switches Hi to 223, the ratchet relay R will take one step, and the pump will run, passing the solution from tank 59 through the treatment units to tank 58, aspreviously described. From there on operation proceeds automatically. I

In Figs. .1- and 4 only the equipment necessary for understanding the fimctioning of the apparatus has been shown. In practical use many refinements well known in the art of treating liquids will advantageously be employed. Thus, especially with automatic operation, it is desirable to arrange automatic refilling of the regenerating solution tanks l2 and 32, as for example, by providing storage tanks h'aving suitably controlled connections with tanks l2 and 32, as disclosed in Staegemann Patent 2,051,155 dated August 18, 1936. The rate of flow of backwash water may be controlled by an arrangement I such as described in Applebaum Patent 1,443,892 dated January 30, 1923. Other flow controlling or limiting device for regulating the fiow rate of the solution being treated and of rinse water may be added. Furthermore, a control mechanism may be used which stops operation of the apparatus when the level in the storage tank 18 has reached a given height.

The ratchet relay may be modified by using a ratchet wheel having twice or four times as many teeth as the number of notches in cam 204 so that regeneration will start when a new batch of solution has been passed two or four times through the treatment units. In this connection it may be noted that the diagram of Fig. 4 is arranged especially for three passes of the water through the treating units prior to regeneration. The ratchet relay solenoid 200 is operated from the same contact strip 3) as the resettin circuit (through switch I93) of the timer T which results in the ratchet relay taking 3 steps during the regeneration process; this has no effect on the operation and causes no difliculty because the 3 steps bring the cam 204 to a position equivalent to that at which it started. If other than 3 passes are required before regeneration, the ratchet relay solenoid 200 and the resetting circuit 'of timer T would be energized from separate contact strips on drum l2l. A device available on the market may be substituted for the ratchet relay which will close a switch after an adjustable number of impulses and then reset itself to its zero or starting position. As another alternative, a switch operated by a, meter measuring the flow of solution being treated may be used. When it is desired to pass the solution but once through the treatment units prior to regeneration the solenoid 200 may be arranged for direct actuation of switch 206. It is to be noted in this connection that the total number of passes required depends not only on the nature and amount of electrolytes in the raw solution and the desired degree of purity oftreated solution, but also on the desired efliciency of utilizing the available capacity of the treating materials. Thus, a given 22 solution may be purified to a given degree in a smaller number of passes if somewhat less emcient utilization of the regenerants is acceptable. When the advantages of staggered regeneration are not needed the ratchet relay may be omitted,

and the arrangement modified so that regeneration is initiated by a meter operated switch when a predetermined quantity of solution, exclusive of solution used in. thesteps of the regenerating cycle, has been admittedto the apparatus, or when the conductivity of the treated solution, even on repeated passage through the treatment units, is neither reduced to any substantial degree, nor has reached the desired low value.

It should be noted here that in manual operation the operator may use the analysis of the solution discharged by pipe 39 as a guide. When the concentration of electrolytes in this solution ceases to drop substantially upon repeated passage through the units without having reached the desired low value, this indicates that the capacity of the materials has been exhausted and that they should be regenerated, whereupon treatment of the batch may be completed by further passage through the treatment units,

Solenoid valves such as shown in Fig. 4 will in general be found satisfactory when both the pressure and the how rate of the solution being treated are relatively low. For high pressures or rates of flow, valves operated by diaphragms or hydraulic pistons may be used, controlled by three or four way so enoid operated valves, or by pilot valve arrangements such as those disclosed in the Pick Patents 2,076,321 and 2,240,163, dated April 6, 1937, and April 29, 1941, respectively, and in Staegemann Patent 2,098,893 dated November 9, 1937. As a further alternative, individual or multiport valves operated by electric motors, with either manual or automatic control, may be employed, as of the type shown in Staegemann Patent 2,051,155 dated August 18, 1936.

If desired, degasifiers such as that shown in storage tank I8, may be installed above the receivin tanks so that COz-is removed from the solution being treated after each passage through the treatment units.

While not economically practical for the purification of sea water, my process will be found well suited for treating brackish water supplies such as those encountered in wells adjacent to the sea shore or to salt deposits, or waters found in the lower reaches of tidal streams, typified by the raw water used in the tests described herein.

The process according to this invention is, however, also useful for the treatment of many chemical process solutions, as shown by the following examples. An aqueous solution containing 15 per cent pentaerythritol and 0.3 per cent sodium formate may be purified by multiple demineralizing; substantially complete removal of the sodium formate, objectionable because it causes a high ash content in the finished pentaerythritol, is obtainable. Electrolytes present in sugar juices may be removed almost completely by multiple demineralizing, thus preventing the formation of excessive amounts of molasses. Multiple demineralizing may also be employed for a more thorough purification of gelatin solutions according to the process disclosed in the Holmes Patent 2,240,116 dated Apri1 29. 1941. Aqueous solutions of glycerol from saponiflcation reactions and of glycols from chlorohydrin hydrolysis contain substantial amounts of sodium chloride which causes difficulties in evaporating the solutions because oi. the formation of deposits on the heating surfaces of evaporators; by multiple demineralizing this obi ectionable salt may beremoved. In treating chemical process solutions the arrangement of pipes and valves will, as a rule, be modified so that water is used in the various steps of the regenerating cycle.

As shown by the tests described herein, the results obtained by the stepwise reduction of the concentration of electrolytes in accordance with my process are indeed startling when compared with prior art methods, both as to quality the treated solution and as to economy in the use of regenerants. This invention thus fills a long felt need in the purification of solutions contaminated by relatively large amounts of electrolytes, especially when substantially complete removal of the electrolytes is desired.

Modifications of either process or apparatus, other than those described or suggested herein, may be made without departing from the spirit of my invention, and reference is, therefore, made to the following claims for a definition of the scope of my invention.

What I claim is:

l. A process of demineralizing an aqueous solution of electrolytes which comprises passing a predetermined substantial volume of said solution successively through cation exchange material and acid removal material and then collecting said volume in a separate receptacle, thereafter re-passing said volume successively through said cation exchange material and said acid removal material and then collecting said volume in a second receptacle, determining the electric conductivity of said solution after it has been re passed through said acid removal material, repeating said re-passing until the electric conductivity of said solution has dropped to a predetermined low value, and then discharging said volume to a point of use.

2. A process of demineralizing an aqueous solution of electrolytes which comprises passing a predetermined substantial volume of said solution successively through cation exchange material and acid removal material and then collecting said volume-in a separate receptacle, thereafter at least once re-passing said volume successively through said cation exchange material and said acid removal material and then collecting said volume in a second receptacle, and finally discharging said volume to a point of use while simultaneously passing another predetermined volume of said solution successively through said cation exchange material and said acid removal material.

3. A process of demineralizing an aqueous solution of electrolytes which comprises at least once passing a predetermined substantial volume of said solution successively through partly exhausted cation exchange material and acid removal material and then collecting said volume in a separate receptacle, then regenerating said materials, thereafter re-passing said volume successively through said regenerated cation exchange material and acid removal material until the concentration of electrolytes in said solution has been reduced to a predetermined low value, and then discharging said volume to a point of use.

4. The process of claim 3 in which said predetermined volume of solution contains a quantity of electrolytes approximately equal to the electrolyte removal capacity, between regenera- 24 tions, of said cation exchange and acid removal materials.

5. The process of claim 3 in which said predetermined volume or solution contains a quantity of electrolytes approximately equal to a proper fraction of which the numerator is unity, of the electrolyte removal capacity, between regenerations, of said cation exchange and acid removal materials.

6. A process of demineralizing an aqueous solution of electrolytes which comprises at least once passing a predetermined substantial volume of said solution successively through cation exchange material and acid removal material and then collecting said volume in a separate receptacle, then regenerating said materials, thereafter re-passing said volume successively through said regenerated cation exchange material and acid removal material, determining the electrolyte content of said solution after it has been passed through said acid removal material, repeating said re-passing until the electrolyte content of said solution has dropped to a predetermined low value, and then discharging said volume to a point of use.

7. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a, tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, a pipe interconnecting both said tanks, and an outlet pipe for said second tank, solution receiving means, a discharge pipe connected with said outlet pipe and-adapted to discharge into said solution receiving means, a service pipe and a return pipe connected with said solution receiving means and leading to a point of use and to said supply pipe, respectively, a valve in said service pipe, a valve in said return pipe, operating means for opening said valve in said service pipe and closing said valve in said return pipe, an electric conductivity meter, electrical circuits for said operating means and said meter whereby said meter is adapted to actuate said operating means, and means for passing through said meter solution flowing through said outlet pipe.

8. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, .a pipe interconnecting both said tanks, and an outlet pipe for said second tank, a pair of receiving tanks, a pair of discharge pipes connected with said outlet pipe and each adapted to discharge into one of said receiving tanks, a valve in each of said discharge pipes, a service pipe leading to a point of use and adapted to be placed into communication with at least one of said receiving tanks, a return pipe connected with said supply pipe and adapted to be placed into communication with at least the other one of said receiving tanks, and means for inducing flow through said return pipe toward said supp y p pe.

9. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, a pipe interconnecting both said tanks, and an outlet pipe for said second tank, a pair of receiving tanks, a pair of discharge pipes connected with said outlet pipe and each adapted to discharge into one of said receiving tanks, a valve in each of said discharge pipes, operating means for opening and closing said valves, volume responsive means on said receiving tanks actuating said operating means to alternately open one and close the other of said valves, a service pipe leading to a point of use, a return pipe leading from said receiving tanks to said supply pipe, and means connected with said receiving tanks for selectively inducing flow therefrom to said service pipe and to said return pipe.

10. Apparatus for demineralizing an aqueous solution of electrolytes which comprises 9, tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, a pipe interconnecting both said tanks, and an outlet pipe for said second tank, a pair of receiving tanks, a pair of discharge pipes connected with said outlet pipe and each adapted to discharge into one of said receiving tanks, a, valve in each of said discharge pipes, a pump, a suction pipe for said pump having a pair of branches each connected with one of said receiving tanks, a valve in each of said branches, operating means for opening and closing all of said valves, volume responsive means on said receiving tanks actuating said operating means to alternately open the valves in one of said discharge pipes and one of said branches and close the valves in the other one of said discharge pipes and the other one of said branches, a valved service pipe leading to a point of use, a valved return pipe connected with said supply pipe, and a discharge pipe for said pump connected with said service pipe and said return pipe.

11. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, a pipe interconnecting both said tanks. and an outlet pipe for said second tank, a pair of receiving tanks, a pair of discharge pipes connected with said outlet pipe and each adapted to discharge into one of said receiving tanks, a valve in each 01' said discharge pipes, a pump, a suction pipe for said pump having a pair of branches each connected with one of said receiving tanks, a valve in each of said branches, a discharge pipe for said pump having a branch leading to a point of use and another branch connected with said supply pipe. and a valve in each oi! said last named branches.

12. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a tank containing cation exchange material, a tank containing acid removal material, piping for said tanks including a supply pipe for the first tank, a pipe interconnecting both said tanks, and an outlet pipe for said second tank, solution receiving means, discharge means connected with said outlet pipe and adapted to discharge into said solution receiving means, a pump having a suction connection communicating with said solution receiving means and a, discharge pipe connected with said supply pipe, a service pipe leading from the apparatus to a point of use, a valve in said service pipe, electrical operating means for opening and closing said valve, an electric conductivity meter, switch means operated by said meter, electrical circuits for said operating means, said meter and said switch whereby said switch is adapted to actuate said electrical operating means, and means for passing through said meter solution flowing through said outlet pipe.

13. Apparatus for demineralizing an aqueous solution of electrolytes which comprises a tank containing cation exchange material, a tank containing acid removal material, receiving means,

piping for said tanks and said receiving means, means in said piping for repassing solution from said receiving means through said tanks back to said receiving means, a float switch in said receiving means, control means for said repassing means, and electrical circuits for said control means, said repassing means and said float switch whereby said float switch is adapted to energize said control means to actuate said repassing means.

14. A process of demineralizing an aqueous solution of electrolytes which comprises passing a predetermined substantial volume of said solution through partly exhausted cation exchange material and acid removal material until the concentration of electrolytes in said volume ceases to drop substantially without having reached a predetermined low value, collecting said volume in a separate receptacle, then interrupting said passing and regenerating said materials, thereafter repeating the passing of said volume until the concentration of electrolytes has reached said predetermined low value, and then discharging said volume to a point of use,

HOWARD L. TIGER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,287,284 Behrman June 23, 1942 2,317,847 Duden Apr. 27, 1943 1,696,369 Trewhitt et al. Dec. 25, 1928 1,775,412 Tannehill Sept. 9, 1930 2,267,841 Riley Dec.'30, 1941 1,954,405 Dotterweich Apr. 10, 1934 948,725 Freeman Feb. 8, 1910 1,800,517 Foster Apr. 14, 1931 1,035,813 Rice Aug. 13, 1912 2,306,720 Fender Dec. 29. 1942 1,759,601 Apeldom May 20, 1930 1,955,693 Turner Apr. 17, 1934 2,209,487 Wagner July 30, 1940 2,315,223 Riche Mar. 30, 1943 1,926,505 Turner Sept. 12, 1933 1,341,790 Edelman June 1, 1920 2,097,779 Shook Nov. 2, 1937 2,366,945

Walker Jan. 9, 1945 

